As is generally known, the basic and most frequently used characters are the numerals from 0 to 9 and the 26 English letters. These numerals and letters are widely used in character input devices used in cell phones, palm PC, etc. There are two techniques used for inputting these characters. One technique consists of providing a corresponding key for each character, as is often used in the keyboard of a palm PC, and the other consists of representing a plurality of characters by a single key, and selecting different characters by pressing the same key multiple times, as is commonly employed by cell phone keypads.
Blind input of information is very import in some applications, such as in dialing a cell phone when driving. Therefore, various input devices using touch guidance have been developed that allow information to be input into a device without the aid of sight. Touch guidance refers to the technique of employing convex or concave shapes in touch-sensitive surfaces that are intended to be contacted by the fingertips. It enables the user to recognize the position of an individual input key through the finger touch, thereby enhancing the user's ability to input information into a device without looking at the device, i.e., blind input. There are two major types of resistive touch sensitive screens (or touch panels) based on the different structural features of the touch sensitive screen, i.e., resistive digital matrix type touch sensitive screens and resistive analog type touch sensitive screens.
The digital matrix type touch sensitive screen is primarily used for individual keypad operation. It comprises an individual easy-touch keypad for a performing specific function, while also permitting the keypad to be switched between on and off. Digital matrix type touch sensitive screens are widely used in display devices for providing public information, industrial equipment control panel and computer input/output devices.
As an input device for character input, the digital matrix type touch sensitive screen provides corresponding keypads for each letter and numeral, therefore the number of keypads corresponds to the number of the letters and numerals that are to be input. The keypads must be physically tapped in order to input information, making it difficult to input the information blindly, or provide a keypad layout that can be miniaturized.
One of the popular applications of analog type touch sensitive screen is the hand-writing board used in palm PCs and mini-notebooks. Existing hand-writing character (including letters and numerals) input technology includes an analog touch panel with thousands (or more) matrix sensor units for sensing input written strokes, an MPU (processing unit) for encoding, decoding and data transmission as well as hand-writing recognition software. Hand-writing recognition accuracy, which has always been a major concern in these hand-writing boards, is made more difficult by the need for the user to write the strokes in a predetermined order in order to be accurately recognized.